QUESTION My husband bought a slow cooker and insists it is much, much cheaper to have it on for eight hours to cook our stews rather than cook for an hour with the main oven (even if this involves much faffing around in the mornings). He's very insistent. Is he right?

ANSWER Slow cookers are, as the name suggests, designed to cook foods such as stews or curries slowly – usually for a minimum of six hours. Depending on the setting, cooking can take as long as 10 hours, making the slow cooker ideal for those who want to be able to leave their food cooking without having to keep an eye on it.

Slow cookers, which have seen sales rise by 55 per cent over the past two years and typically cost about $40 to buy, might be more practical for those with a busy schedule, but is it cheaper to use than an oven? Consumer price comparison site uSwitch says that the microwave is the most energy-efficient way to cook food, followed by a hob and lastly an oven.

"Slow cookers can also be an energy-efficient option – they use just a little more energy than a traditional light bulb," the website says. The Centre for Sustainable Energy (www.cse.org.uk) estimates the average electricity usage of an electric oven between 2-2.2kWh, while a microwave uses between 0.6-1.5kWh.

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A slow cooker uses approximately 0.7kWh over the eight hours. Money-saving website goodtoknow.co.uk says the electric oven is the most expensive appliance to use in the home. Using it for an hour each day will cost £2.46 ($4.55) a week, or £127.92 ($236.59) over a year. Other websites would agree that the oven uses far more energy than other cooking appliances, like microwaves and slow cookers.

Energy comparison website Uswitch says: "Slow cookers can also be an energy-efficient option – they use just a little more energy than a traditional light bulb, and you can leave your food to cook slowly while you get on with other things." It is undeniable that microwaves are the cheapest way to cook food, but a stew needs to, well, stew. So a microwave is out of the equation. Between an oven and a slow cooker, which would be cheapest?

Electricity costs around 15p (28¢) per kWh, so using an oven for an hour to cook your stew will cost around 30p (56¢) – depending on your temperature. A slow cooker, which uses around 0.7kWh over the eight hours cooking time as an average of , will cost a third of the price, at 10.5p (18¢).

Of course, it depends on the temperature you cook at. We've assumed that the slow cooker is on a low setting – a little under 100w – and that the oven is also turned down.

So in answer to the question, the slow cooker comes out as the cheaper appliance to use, as well as being a useful way to cook if you have a busy schedule. Although it requires – as you say – more faffing in the mornings, it does make your stew tastier than if it was cooked in the oven, and saves you a few pence.